With a fresh infusion of $4 million from Comcast Interactive Capital, which it raised recently in a series B financing (with previous investor BlueRun also pitching in), hyperlocal places database Fwix is pushing out a major upgrade to its developer API today. Fwix is creating an open database of places in partnership with Factual . Developers will be able to pull data about millions of places into their own apps, and edit the places as well by adding their own data or content. Fwix started focusing on becoming more of a places database last year , but its API was clunky. Nevertheless, it served 20 million API calls in March, up from 11 million in February. Now with the new developer API, it will be easier to associate places with content such as news articles, Tweets, and check-ins. The API also includes an advertising layer which plugs into various mobile ad networks and geo-specific offers, including ones from Groupon, LivingSocial, YellowPages.com, and Gilt City.